Here are some pics. Original booster with 68 Mustang (took it out of my car to test) MC. Other pics are the booster and MC that came in the box.
For everybodys' education, what was pictured appears to be a '64 version with stamped steel front housing and a band clamp holding the halves together: this is what's often used for a replacement. OEM was the Midland-Ross "10-screw" booster with cast aluminum front housing. Pictures below are of the OEM Midland-Ross brake booster.
Have you tried looking in the 1963 Modified/Custom section of Vintage Thunderbird Club International's Forum?
https://www.vintagethunderbirdclub.net/phpBB3/viewforum.php?f=23
Link below are to articles found by searching for disc brake conversion master cylinder booster
https://www.vintagethunderbirdclub....disc+brake+conversion+master+cylinder+booster